Physical Chemistry Communications, Volume 3 Issue 1, April 2016 www.bacpl.org/j/pcc
Construction of Hierarchical Pores Membrane by Growing Metal Organic Frameworks on Copper Foams Wen Zhang*1, Liqiang Zhang1, Hui Wang2, Zhiguo Qu2 1 School of Science, Xiʹan Jiaotong University, Xiʹan, Shaanxi 710049, China 2 MOE Key Laboratory of Thermo‐Fluid Science and Engineering, School of Energy and Power Engineering, Xiʹan Jiaotong University, Xiʹan, Shaanxi 710049, China *1
zhangwen@mail.xjtu.edu.cn.edu
Abstract A series of hierarchical pores Cu–BTC membrane was obtained by electrochemical method when copper foams with different pore‐density were used as the electrodes. Scanning electron microscope (SEM) and X‐ray diffraction (XRD) were used to characterize the morphology and structure of the coating; while their specific surface areas were obtained by nitrogen adsorption. Key factors in the process of electrochemical synthesis such as current intensity, temperature, time and ligand concentration were investigated systematically to find out the optimal conditions based on synthesis yield and morphology of the samples. The mechanisms of Cu‐BTC formed on the surface of copper foams were discussed. The effective thermal conductivity of Cu‐BTC/Cu‐Foam film was higher than that of pure Cu‐BTC. This paper provides a simple and reproducible way to construct hierarchical pores membrane for potential industrial applications on separation and adsorption. Keywords Metal Organic Frameworks; Membrane; Electrochemical Method; Cu‐BTC
Introduction Metal organic frameworks (MOFs) have attracted a lot of attention in recent years because of their high surface areas, regular pore sizes and pore shapes, and potential for functionalization. They have many applications in different fields such as gas adsorption[1], catalysis[2] and sensors[3]. Besides, using as powder, many of the applications require the MOFs to be deposited on various surface, such as membranes for gas adsorption, thin film in luminescent sensors or microelectronic devices[4]. However, these requirements have some difficulties in that most MOFs are made as brittle crystals or insoluble powders that cannot be directly applied to general surface‐ processing techniques. In addition, the thermal conductivity of the powder is so low that the structure of the MOFs might be collapse when it is used for gas adsorption since the adsorption for gas is exothermic reaction[5]. To overcome these difficulties, membranes or thin‐films growth techniques, which are initially developed for zeolites and molecular materials such as seeded and epitaxial growth, have also been applied to MOFs recently[6]. While the central atom of the MOFs is the metal ions, the electrochemical synthesis method have enjoyed tremendous popularity in recent years. The principle of the electrochemical synthesis relies on supplying the metal ion by anodic dissolution in a synthesis mixture that contains the organic linker and an electrolyte. The metal ion is not supplied as salt but by oxidation of the electrode. The energy required to oxidize the anode can be supplied in amperometric or potentiometric mode. This experiment employed the amperometric mode, that is to say, the voltage is fixed and current can be used to measure the reaction rate expressed as the speed at which the metal ions are dissolved. A general advantage of electrochemical synthesis is that it allows synthesis under a milder condition than typical solvothermal or microwave synthesis. It is performed under atmospheric pressure and relatively low temperature. It also reduces the time required for certain synthesis: whereas solvothermal or microwave synthesis might take hours or days, electrochemical synthesis can produce the material within minutes or hours. Moreover, electrochemical synthesis
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